Cut perfect circles with a band saw

Photo 1: Attach the runner

Cut 3/4-in. plywood to 16 x 24 in. Draw centerlines on both sides,
then glue and pin the runner to the bottom. Send the jig through
the blade until you reach the centerline, then clamp the auxiliary
fence to the jigsaw fence.

Photo 2: Finish the jig

Tap a nail through the hole, then flip the jig over. Drill a hole in the
middle of the blank and prop the circle stock over the nail shank.

Cutting perfect circles is easy with a band saw—as long as
you take a half hour to build yourself a cutting jig. I've cut
circles with radiuses ranging from a few inches to a couple
of feet. The only limit is the distance from the fence to the
saw blade.

Use any 3/4-in. plywood to make the jig, and attach a runner
to the underside that fits in the band saw's miter gauge
slot. That will hold everything steady while you turn the
actual circle stock through the blade. Then make yourself an
auxiliary fence from another piece of 3/4-in. plywood as
shown. Send the jig through the blade to create the saw kerf,
then shut off the saw when the
blade reaches the centerline and
lock the fence about 1/8 in. away from
the jig. Clamp the auxiliary fence to the band saw fence with
the stop against the edge of the jig. Hold it slightly above the
jig so the jig will slide easily beneath it. The auxiliary fence
not only stops the jig at the right spot for turning circles but
also keeps the jig from tipping up from the band saw table.

Cutting is simple. You'll need to choose narrow blades for
small circles. Push the jig with the mounted cutting blank
until you reach the stop and then just twist the blank
through the blade. You'll have a small amount of cleanup to
do where the cut starts and stops. You're done.

Jig and Auxiliary Fence

The auxiliary fence provides a
positive stop at the jig
centerline and keeps
the jig from tipping
during the cut.